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4 rules-of-fractions1640

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4 rules-of-fractions1640

  1. 1.     This presentation will help you to: add subtract multiply and divide fractions
  2. 2. To add fractions together the denominator (the bottom bit) must be the same. Example 1 2 + = 8 8
  3. 3. To add fractions together the denominator (the bottom bit) must be the same. Example 1 2 1+ 2 + = = 8 8 8
  4. 4. To add fractions together the denominator (the bottom bit) must be the same. Example 1 2 1+ 2 3 + = = 8 8 8 8
  5. 5. Click to see the next slide to reveal the answers. 1 1 + = 3 3 2 1 + = 2. 4 4 2 4 + = 3. 7 7 3 7 4. + = 12 12 1.
  6. 6. 1. 2 1 1 + = 3 3 3 3. 2 4 6 + = 7 7 7 2. 2 1 3 + = 4 4 4 4. 3 7 10 + = 12 12 12
  7. 7. Subtracting fractions To subtract fractions the denominator (the bottom bit) must be the same. Example 3 2 − = 8 8
  8. 8. Subtracting fractions To subtract fractions the denominator (the bottom bit) must be the same. Example 3 2 3− 2 − = = 8 8 8
  9. 9. Subtracting fractions To subtract fractions the denominator (the bottom bit) must be the same. Example 3 2 3− 2 1 − = = 8 8 8 8
  10. 10. Now try these Click on the next slide to reveal the answers. 1. 3. 2 1 − = 3 3 4 3 − = 7 7 2. 4. 2 1 − = 4 4 7 3 − = 12 12
  11. 11. Now try these . 1. 3. 2 1 1 − = 3 3 3 4 3 1 − = 7 7 7 2. 4. 2 1 1 − = 4 4 4 7 3 4 − = 12 12 12
  12. 12. Multiplying fractions To multiply fractions we multiply the tops and multiply the bottoms Top x Top Bottom x Bottom
  13. 13. Multiplying fractions Example 1 1 × = 2 3
  14. 14. Multiplying fractions Example 1 1 1× 1 = × = 2 3 2×3
  15. 15. Multiplying fractions Example 1 1 1× 1 1 = × = 2 3 2×3 6
  16. 16. Now try these Click on the next slide to reveal the answers. 1. 3. 1 1 × = 3 3 2 4 × = 4 5 2. 4. 2 1 × = 4 4 1 3 × = 3 5
  17. 17. Now try these . 1. 3. 1 1 1 × = 3 3 9 2 4 8 × = 4 5 20 2. 4. 2 1 2 × = 4 4 16 1 3 3 × = 3 5 15
  18. 18. Dividing fractions Once you know a simple trick, dividing is as easy as multiplying! • Turn the second fraction upside down • Change the divide to multiply • Then multiply!
  19. 19. Dividing fractions Example 1 1 ÷ =? 6 3 •Turn the second fraction upside down 1 3 ÷ 6 1
  20. 20. Dividing fractions Example 1 1 ÷ =? 6 3 •Turn the second fraction upside down 1 3 ÷ 6 1 •Change the divide into a multiply 1 3 × 6 1
  21. 21. Dividing fractions Example 1 1 ÷ =? 6 3 •Turn the second fraction upside down 1 3 ÷ 6 1 •Change the divide into a multiply 1 3 × 6 1 •Then multiply 1 3 1× 3 × = = 6 1 6 ×1
  22. 22. Dividing fractions Example 1 1 ÷ =? 6 3 •Turn the second fraction upside down 1 3 ÷ 6 1 •Change the divide into a multiply 1 3 × 6 1 •Then multiply 1 3 1× 3 3 × = = 6 1 6 ×1 6
  23. 23. Now try these Click on the next screen to reveal the answers. 1. 3. 1 1 ÷ = 3 2 1 2 ÷ = 4 6 2. 4. 1 2 ÷ = 4 3 1 4 ÷ = 2 5
  24. 24. Now try these 1. 3. 1 1 2 ÷ = 3 2 3 1 2 6 ÷ = 4 6 8 2. 4. 1 2 3 ÷ = 4 3 8 1 4 5 ÷ = 2 5 8
  25. 25. To add or subtract fractions together the denominator (the bottom bit) must be the same. So, sometimes we have to change the bottoms to make them the same. In “maths-speak” we say we must get common denominators
  26. 26. To get a common denominator we have to: 1. Multiply the bottoms together. 2. Then multiply the top bit by the correct number to get an equivalent fraction
  27. 27. For example 1 1 − =? 2 3
  28. 28. For example 1 1 − =? 2 3 1. Multiply the bottoms together 2×3 = 6
  29. 29. For example 1 1 − =? 2 3 2. Write the two fractions as sixths 1 ? = 2 6 1 ? = 3 6
  30. 30. For example 1 1 − =? 2 3 To get ½ into sixths we have multiplied the bottom (2) by 3. To get an equivalent fraction we need to multiply the top by 3 also
  31. 31. For example 1 1 − =? 2 3 To get ½ into sixths we have multiplied the bottom (2) by 3. To get an equivalent fraction we need to multiply the top by 3 also 1 1× 3 3 = = 2 6 6
  32. 32. For example 1 1 − =? 2 3 To get 1/3 into sixths we have multiplied the bottom (3) by 2. To get an equivalent fraction we need to multiply the top by 2 also
  33. 33. For example 1 1 − =? 2 3 To get 1/3 into sixths we have multiplied the bottom (3) by 2. To get an equivalent fraction we need to multiply the top by 2 also 1 1× 2 2 = = 3 6 6
  34. 34. For example 1 1 − =? 2 3 We can now rewrite 1 1 − = 2 3
  35. 35. For example 1 1 − =? 2 3 We can now rewrite 1 1 3 2 − = − 2 3 6 6
  36. 36. For example 1 1 − =? 2 3 We can now rewrite 1 1 3 2 3− 2 − = − = 6 2 3 6 6
  37. 37. For example 1 1 − =? 2 3 We can now rewrite 1 1 3 2 3− 2 − = − = 6 2 3 6 6 1 = 6
  38. 38. This is what we have done: 1 1 ? ? − = − 2 3 6 6 1. Multiply the bottoms
  39. 39. This is what we have done: 1 1 ? ? 1× 3 ? − = − = − 2 3 6 6 6 6 1. Multiply the bottoms 2.Cross multiply
  40. 40. This is what we have done: 1 1 ? ? 1× 3 ? 3 1× 2 − = − = − = − 2 3 6 6 6 6 6 6 1. Multiply the bottoms 2.Cross multiply
  41. 41. This is what we have done: 1 1 ? ? 1× 3 ? 3 1× 2 3 2 − = − = = − − = − 2 3 6 6 6 6 6 6 6 6 1. Multiply the bottoms 2.Cross multiply
  42. 42. Now try these Click on the next slide to reveal the answers. 1. 3. 1 1 + = 3 2 3 1 14 − = 4 6 24 2. 4. 1 2 + = 4 3 4 1 + = 5 2
  43. 43. Now try these 1. 3. 5 1 1 + = 6 3 2 3 1 14 7 − = = 4 6 24 12 2. 4. 1 2 11 + = 4 3 12 3 4 1 + = 5 2 10
  44. 44. Go to:  BBC Bitesize Maths Revision site by clicking here:

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